Bartter syndrome in Costa Rica: a description of 20 cases.

Bartter syndrome involves an overlapping set of closely related renal tubular disorders which can be subdivided into at least three clinical phenotypes: (1) classic Bartter syndrome (2) Gitelman syndrome, and (3) a neonatal variant of Bartter syndrome. In contrast to classic Bartter syndrome and Gitelman syndrome, the neonatal variant of Bartter syndrome has both the features of renal tubular hypokalemic alkalosis as well as profound systemic manifestations. Specifically, neonatal Bartter syndrome is characterized by intrauterine polyhydramnios, premature delivery, and life-threatening episodes of fever and dehydration. Most of these infants also have severe hypercalciuria with associated nephrocalcinosis and osteopenia. Over a 22-year period, 20 Costa Rican patients with a congenital syndrome that resembles neonatal Bartter syndrome have been identified and characterized. While these patients exhibit some of the clinical characteristics previously described for neonatal Bartter syndrome, this cohort also has a set of distinct features. They are predominantly female, have a later age of diagnosis, manifest a relatively unique set of physical traits, and appear to have milder clinical disease. Given these differences, it will be important to apply the emerging molecular tools to determine whether the phenotypic variability indicates genetic heterogeneity in neonatal-onset Bartter syndrome.